German Patent No. 195 00 706 describes a fuel injector. A stroke translator or path transformer is provided that converts a relatively small regulating distance of the actuator, for example a piezoactuator, into a larger stroke of the valve needle. Here, the extension of the actuator is introduced into an amplification (boost) chamber via a working piston of the stroke translator, and is transmitted via a lifting piston to the valve needle, which executes a stroke that is enlarged in relation to the piston surface that limits the amplification chamber at the face. In order to compensate temperature influences, wear, and manufacturing tolerances on the regulation path of the actuator, the amplification chamber has a defined leakage that is realized by an annular gap between the piston and a wall of the valve housing, and that has a resistance to flow that is high enough that the movements of the actuator are transmitted in essentially undampened fashion to the valve needle. The fuel itself diesel fuel in the case of German Patent No. 195 00 706—is used as the hydraulic medium for the stroke translation.
The fuel injector described in German Patent No. 195 00 706 has the disadvantage that, in particular at high speeds of the internal combustion engine, a high degree of heat loss occurs in the area of the annular gap, due to the frictional forces that occur when the actuator is actuated. The load and wear of the piston and of the valve housing wall in the area of the annular gap have an adverse effect on the functioning of the temperature compensation, and reduce the lifespan of the fuel injector.
Moreover, the conventional temperature compensation device has a high constructive expense, which increases the manufacturing costs of the fuel injector. A further disadvantage is that the leakage defined by the annular gap can be modified only by modifying the manufacturing process, so that the temperature compensation cannot be adapted to the specific requirements of use of the fuel injector.